Polymicrobial acute respiratory infections in a hospital-based pediatric population.

BACKGROUND: The clinical impact of polymicrobial respiratory infections remains uncertain. Previous reports are contradictory regarding an association with severe disease. METHODS: Three hundred forty-six specimens from children with acute respiratory illness identified at the University of Iowa Hospitals and Clinics Clinical Microbiology Laboratory were evaluated by direct immunofluorescent assay and/or viral culture by Clinical Microbiology Laboratory and later by molecular study for the presence of influenza, parainfluenza, respiratory syncytial virus, adenovirus, human metapneumovirus, rhinovirus and human bocavirus. Demographic and clinical data were abstracted from medical records. RESULTS: Multiple viruses were detected in 46 (21.7%) of 212 virus-positive specimens with the most frequent virus-virus combinations being HRV-respiratory syncytial virus (n = 12), HRV-human bocavirus (n = 6) and HRV-parainfluenza virus 3 (n = 4). Risk factors for coinfection included male gender (OR [odds ratio]: 1.70, 95% confidence interval [CI]: 0.83-3.46), 6 months to 1 year age (OR: 2.15, 95% CI: 0.75-6.19) and history of immunosuppression (OR: 2.05, 95% CI: 0.99-4.23). Children with viral coinfections were less likely than children with single virus infections to be admitted to an intensive care unit (OR: 0.32, 95% CI: 0.08-1.27); however, this may be explained by undetected viral-bacterial coinfections. CONCLUSIONS: HRV, respiratory syncytial virus, human bocavirus, and polymicrobial infections were prevalent in this study. Although the cross-sectional design could not easily examine polymicrobial infection and disease severity, prospective, population-based research regarding the clinical impact of such infections is warranted.

Emergent US adenovirus 3 strains associated with an epidemic and serious disease.

BACKGROUND: Adenovirus type 3 (HAdV3) is one of the most prevalent serotypes detected globally. Variants of HAdV3 have been associated with outbreaks of severe disease. OBJECTIVES: To better understand genetic diversity of circulating HAdV3s and examine risk factors for severe disease. STUDY DESIGN: Restriction enzyme analysis for genomic characterization of clinical HAdV3 isolates detected by 15 collaborative US laboratories during the period July 2004 to May 2007. Multivariate modeling was employed for statistical analyses. RESULTS: The most common HAdV3 types of 516 isolates studied were HAdV3a2 (36.9%), HAdV3a50 (27.1%), HAdV3a51 (18.0%), and HAdV3a17 (4.6%). Non-HAdV3a genome types were rare (1.2%). HAdV3a50 and HAdV3a51 are newly described variants which became more prevalent in 2006 and 2007 and have been associated with at least one epidemic. Their uniqueness was determined by specific banding profiles generated by digests with endonucleases BclI, BglII, and HindIII. Multivariable risk factor modeling demonstrated that children under 2 years of age (OR=2.7; 95%CI 1.6-4.6), persons with chronic disease (OR=5.1; 95%CI 2.6-9.8), persons infected with HAdV3a2 (OR=3.0; 95%CI 1.5-6.0), with HAdV3a50 (OR=2.5; 95%CI 1.2-5.2), or with multiple or rare strains (OR=2.8; 95%CI 1.3-6.5) were at increased risk of severe HAdV3 clinical disease. CONCLUSIONS: In the study period considerable genetic diversity was found among US clinical HAdV3 strains. Novel variants emerged and became prevalent. One such emergent strain may be associated with more severe clinical disease.

Molecular typing of clinical adenovirus specimens by an algorithm which permits detection of adenovirus coinfections and intermediate adenovirus strains.

BACKGROUND: Epidemiological data suggest that clinical outcomes of human adenovirus (HAdV) infection may be influenced by virus serotype, coinfection with multiple strains, or infection with novel intermediate strains. In this report, we propose a clinical algorithm for detecting HAdV coinfection and intermediate strains. STUDY DESIGN: We PCR amplified and sequenced subregions of the hexon and fiber genes of 342 HAdV-positive clinical specimens obtained from 14 surveillance laboratories. Sequences were then compared with those from 52 HAdV prototypic strains. HAdV-positive specimens that showed nucleotide sequence identity with a corresponding prototype strain were designated as being of that strain. When hexon and fiber gene sequences disagreed, or sequence identity was low, the specimens were further characterized by viral culture, plaque purification, repeat PCR with sequencing, and genome restriction enzyme digest analysis. RESULTS: Of the 342 HAdV-positive clinical specimens, 328 (95.9%) were single HAdV strain infections, 12 (3.5%) were coinfections, and 2 (0.6%) had intermediate strains. Coinfected specimens and intermediate HAdV strains considered together were more likely to be associated with severe illness compared to other HAdV-positive specimens (OR=3.8; 95% CI=1.2-11.9). CONCLUSIONS: The majority of severe cases of HAdV illness cases occurred among immunocompromised patients. The analytic algorithm we describe here can be used to screen clinical specimens for evidence of HAdV coinfection and novel intermediate HAdV strains. This algorithm may be especially useful in investigating HAdV outbreaks and clusters of unusually severe HAdV disease.

Adenovirus type 3 outbreak in connecticut associated with a novel variant.

An adenovirus outbreak occurred in New Haven, Connecticut in 2006-2007. Molecular typing revealed a twofold increase in adenovirus type 3 infections. Restriction enzyme analysis (REA) indicated that the CT outbreak was largely due to a marked increase in the novel Ad3a51 strain. This outbreak represents the first detection of Ad3a51 in the United States. While most infections were mild, children under 3 were at increased risk for severe disease and one patient with underlying disease died.

Genotype prevalence and risk factors for severe clinical adenovirus infection, United States 2004-2006.

BACKGROUND: Recently, epidemiological and clinical data have revealed important changes with regard to clinical adenovirus infection, including alterations in antigenic presentation, geographical distribution, and virulence of the virus. METHODS: In an effort to better understand the epidemiology of clinical adenovirus infection in the United States, we adopted a new molecular adenovirus typing technique to study clinical adenovirus isolates collected from 22 medical facilities over a 25-month period during 2004-2006. A hexon gene sequence typing method was used to characterize 2237 clinical adenovirus-positive specimens, comparing their sequences with those of the 51 currently recognized prototype human adenovirus strains. In a blinded comparison, this method performed well and was much faster than the classic serologic typing method. RESULTS: Among civilians, the most prevalent adenovirus types were types 3 (prevalence, 34.6%), 2 (24.3%), 1 (17.7%), and 5 (5.3%). Among military trainees, the most prevalent types were types 4 (prevalence, 92.8%), 3 (2.6%), and 21 (2.4%). CONCLUSIONS: For both populations, we observed a statistically significant increasing trend of adenovirus type 21 detection over time. Among adenovirus isolates recovered from specimens from civilians, 50% were associated with hospitalization, 19.6% with a chronic disease condition, 11% with a bone marrow or solid organ transplantation, 7.4% with intensive care unit stay, and 4.2% with a cancer diagnosis. Multivariable risk factor modeling for adenovirus disease severity found that age <7 years (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.4-7.4), chronic disease (OR, 3.6; 95% CI, 2.6-5.1), recent transplantation (OR, 2.7; 95% CI, 1.3-5.2), and adenovirus type 5 (OR, 2.7; 95% CI, 1.5-4.7) or type 21 infection (OR, 7.6; 95% CI, 2.6-22.3) increased the risk of severe disease.

Human metapneumovirus, Peru.

We retrospectively studied 420 pharyngeal swab specimens collected from Peruvian and Argentinean patients with influenzalike illness in 2002 and 2003 for evidence of human metapneumovirus (HMPV). Twelve specimens (2.3%) were positive by multiple assays. Six specimens yielded HMPV isolates. Four of the 6 isolates were of the uncommon B1 genotype.